No puedo actualizar las aplicaciones porque me dice que tengo facturas pendientes

See -> Resolve a problem with your payment method

If your payment method has expired, declined or failed, or a message says "There is a Billing Problem with a Previous Purchase"

See the following Apple articles:

Add a payment method to your Apple ID

Add a payment method to your Apple ID – Apple Support (UK)

If you need to change or update your Apple ID payment method

If you need to change or update your Apple ID payment method - Apple Support

Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

fyi: Not all credit & debit cards seem to work with App Store / iTunes Store, try a different one, or preferably a credit card. If your card is not accepted as a paymenf method, you need to contact your bank.

If you still need help, get support from Apple directly -> Get Support or call Apple in your region see -> Contact Apple for support and service or check -> here for more support and assistance.